DE69629814T2 - Volume Limit - Google Patents

Abstract

For limiting the signal transmitted to the human ear in dependency on an incoming acoustical signal, there is provided a signal processor 3, the output of which acts on an output transducer and on a calculator unit 7 which calculates according to a preselected model the psychoacoustical entity loudness of the incoming acoustic signal. The loudness, thus calculated, is compared with a predetermined loudness level MAL and according to the result of such comparison, parameters at the processor unit 3 are varied so as to restrict the transmitted loudness on the MAL level. <IMAGE>

Description

The present invention is based on a method of limiting what is transmitted to the human ear Signal depending directed by an incoming switching signal and is also on a hearing directed, which has an input sound / electrical converter, whose output with the input of a signal processor unit a controllable spectral transmission characteristic is operatively connected, the output of this processor unit with operatively connected to the input of an output transducer for the human ear is.

definition of loudness

• – E. Zwicker, "Psychoakustik", Springer-Verlag Berlin, Hochschultext, 1982;
• – A. Leijon "Hearing Aid Gain for Loudness-Density Normalization in Cochlear Hearing Losses with Impaired Frequency Resolution", Ear and Hearing, Bd. 12, Nr. 4, 1990;
• – EP-0 661 905 des gleichen Anmelders wie die folgende Anmeldung;
• – H. Dillon, "Compression? Yes, but for low or high frequencies, for low or high intensities, and with what response times?", Ear and Hearing, Bd. 17, Nr. 4, 1996.

The loudness of a sound signal is a psychoacoustic variable. In order to quantify the loudness that a single standard person perceives as a function of incoming sound signals, several models have been developed. For example, reference is made to

• - E. Zwicker, "Psychoacoustics", Springer-Verlag Berlin, university text, 1982;
• - A. Leijon "Hearing Aid Gain for Loudness-Density Normalization in Cochlear Hearing Losses with Impaired Frequency Resolution", Ear and Hearing, Vol. 12, No. 4, 1990;
• - EP-0 661 905 by the same applicant as the following application;
• - H. Dillon, "Compression? Yes, but for low or high frequencies, for low or high intensities, and with what response times?", Ear and Hearing, Vol. 17, No. 4, 1996.

All models used for calculation of the loudness impression are used, apply the concept of a Auditory filter bank and divide a sound signal into spectral bands. In psychoacoustics these filter tapes the critical bands called. They deliver one on a psychoacoustic frequency scale constant filter bandwidth according to Bark (Zwicker) or ERB (B. Moore, "Perceptual consequences of cochlear damage ", Oxford Psychology Series 28, Oxford University Press, 1995).

In a first step, the Auditory filter bank a transformation of the physical spectrum into a so-called Excitation patterns. The arousal pattern, the initial response of the Auditory filter bank, can for arbitrary signal spectra are calculated, the method in the Literature are described (Moore).

In the second step, the contributions in each critical volume that of the respective cochlear excitation delivered loudness calculated which is called the specific loudness will and that over all bands the hearing filter bank is further integrated or summed up what the overall loudness of the Provides signal spectrum.

The parameters of the loudness model are for normal hearing known and standardized and can for impaired People changed accordingly be, procedures for the measurement of loudness model parameters of individual people have been proposed (S. Launer, "Loudness Perception in Listeners with Sensorineural hearing impairment ", Dissertation, Department of Physics, University of Oldenburg, Germany, 1995).

Regarding the standard of normal hearing reference is made to ISO 226, "Acoustics - normal equal-loudness contours ", International Organization for Standardization, Geneva 1987.

L(P): Lautheit
L'_k(S_k(f),P_k): spezifische Lautheit, Lautheitsbeitrag des Frequenzbands Nr. k
P_k: bandspezifische Modellparameter
S_k(f): das physikalische Spektrum des Signals im Band Nr. k aus dem physikalischen Spektrum S(f).
P: die Entität der Parameter P_k.The loudness of a sound signal spectrum can be expressed in general:

L (P): loudness
L ' _k (S _k (f), P _k ): specific loudness, loudness contribution of frequency band No. k
P _k : band-specific model parameters
S _k (f): the physical spectrum of the signal in band no. K from the physical spectrum S (f).
P: the entity of the parameters P _k .

In this literature there is loudness rather than with L, L 'often with the symbol N or N '.

Because of security and comfort it is known that hearing aids are a system require that the performance of the signals be limited because special the sound print for Electrical / sound output transducer that is transmitted to the human ear depends on the incoming sound signals. Even under a wider one Aspect and thus under the aspect of protecting human Ear in a very noisy environment is the need for one such limitation obviously.

In today's hearing aid technology, there are two limitation techniques known d. H. the so-called "tip clipping (PC)" technique and the so-called Technique of "automatic gain control (AGC) "(H. Dillon).

According to the PC technology, the transmitted power clamped to a threshold. Obviously, this has the disadvantage that a considerable amount harmonic disturbance occurs as soon as the transmitted signal reaches the cut-off level. So it is this with hearing aids Technology common to provide the limit threshold value adjustable.

According to AGC technology, the transmitted power is measured in comparison to an approved level and the hearing aid gain is set according to the result of this comparison as by feedback control. It has also been proposed to subdivide the transmission characteristics of the hearing aid into different spectral bands, to set a specific threshold value for each spectral band, and the Limit transmitted power separately in each frequency band by the AGC.

All of these approaches depart from the attempt from the power level according to a Limit performance limits at which hearing becomes uncomfortable or even harmful. It is known that people do not have physical performance received as a special sound pressure level, but the psychoacoustic Loudness received, and that due to excessive loudness a special one Discomfort is caused.

Following this realization, it is an object of the present invention, one as stated above To provide a method and a device as specified above, the signal transmitted to the human ear according to human perception limit of sound signals.

• – Vorsehen einer begrenzenden Hörvorrichtung, die aus einem eingehenden Schallsignal ein Ausgangssignal erzeugt, das an das menschliche Ohr mit einer steuerbaren Übertragungscharakteristik übertragen wird;
• – Speichern eines Schwellenwertes in der Vorrichtung;
• – Erzeugen eines von der Lautheit des an das menschliche Ohr übertragenen Signals abhängenden Signals in der Vorrichtung;
• – Verringern der Lautstärke des an das Ohr übertragenen Signals durch automatisches Einstellen von Parametern der Übertragungscharakteristik, die die Lautheit des an das menschliche Ohr übertragenen Signals bestimmen, sobald das von der Lautheit des übertragenen Signals abhängende Signal den Schwellenwert erreicht.

Deviating from a procedure as given above, this task is solved by:

• - Providing a limiting hearing device that generates an output signal from an incoming sound signal, which is transmitted to the human ear with a controllable transmission characteristic;
• Storing a threshold value in the device;
• Generating in the device a signal dependent on the loudness of the signal transmitted to the human ear;
• Reducing the volume of the signal transmitted to the ear by automatically setting parameters of the transmission characteristic which determine the loudness of the signal transmitted to the human ear as soon as the signal dependent on the loudness of the transmitted signal reaches the threshold value.

In contrast, and especially in relation to the According to the AGC, the loudness of the transmitted signal is monitored as a test entity or modeled. This is done by applying a model that calculates the perceived loudness from a spectrum, which represents an acoustic signal, and it is this loudness that has a pleasant loudness threshold which is a standard and / or which is compared individually Experiments are determined to limit the loudness of the transmitted signal. In a preferred embodiment the loudness reduction is carried out by the fact that the loudness contributions in all critical bands or individually in a dominant part of the critical bands or according to an equal Percentage is reduced.

In addition, the method according to the invention, without limiting the present invention, mainly in a hearing aid than that limiting device applied.

In a further preferred embodiment of the method according to the invention becomes the spectral transmission characteristic the device depending the loudness perceived by a single person which the hearing aid wears, and dependent on from the reference loudness by a single standard person perceived without hearing aid would, set or permanently set.

The hearing device according to the invention in the way is constructed in such a way that it fulfills the task mentioned above a presettable memory unit and an output converter with an input that is operatively connected to the output of the processor unit is, wherein the arithmetic unit generates an output signal from depends on the loudness of a sound signal caused by the signal at the input represents the output converter becomes. The output of the presettable storage unit and the output of the computing unit with the respective inputs of a comparison unit operatively connected, whose output with the setting inputs in the Signal processor unit is operatively connected, making its transmission characteristic is set automatically. This is done by setting the transmission characteristics the signal processor unit the resulting loudness as they according to one pre-selected Model monitored by the computing unit is reduced accordingly until it z. B. in a negative feedback control loop or by iteration, as preset in the storage unit Value reached that is the loudness level of the maximum acceptable loudness MAL corresponds.

The invention and further embodiments will be understood by those skilled in the art upon reading the detailed description and the following claims Roger that. The figures show:

1 a greatly simplified functional block diagram / signal flow chart of a limiting device according to the invention, which carries out this method according to the invention,

2 3 shows a functional block diagram / signal flow diagram of a hearing aid which is constructed in accordance with the present invention, in the form preferred today,

3 heuristically the spectrum of a signal at the output of the device according to the invention which leads to an over-loudness and is limited to a loudness below or at the MAL.

According to 1 a limiting device according to the invention comprises an input sound / electrical converter 1 whose output is connected to the input of a processor unit 3 is operatively connected, the output of which is connected to an output converter, as shown with an output electrical / mechanical converter 5 , is connected.

The signal processor unit 3 has a transmission characteristic T (f) as a function of the frequency f (in Hz, Bark or ERB), which, as is exemplary with the characteristics in the unit block 3 shown is adjustable at the control inputs E ₃ . As will be described later in connection with the preferred embodiment, the transfer function T is preferably performed by a bank of filters, e.g. B. in a parallel structure, each filter in a certain spectral band, e.g. B. is defined according to the critical bands of human hearing, and thus preferably acts.

The input of a computing unit 7 is operatively connected to the output of the processor unit 3 and calculates the loudness L (S, P) of the unit output 3 , This unit carries out the calculation of the loudness L according to a selected loudness model, as it is e.g. B. is disclosed in EP-0 661 905 or in S. Launer, the two references to loudness modeling are inserted in the present description.

The selected model parameters P are in the computing unit 7 entered. The output signal of the computing unit 7 , which represents loudness as a psychoacoustic entity, becomes an input to a comparison unit 9 fed, the other input with a storage unit 11 that is loaded with a MAL value either by a single person or as a general standard safety value. If the loudness L value is as determined by the unit 7 is calculated, the MAL value is reached or exceeded, the comparator unit acts 9 on an adjustment unit 13 , in which the transfer function control signals applied to E ₃ are set in such a way that the loudness L (S, P) as determined by the computing unit 7 is modeled, is reduced.

Thus the actual Loudness as transmitted to the human ear and thus perceived is being supervised and that which is transmitted to the human ear Signal decreases once the monitored Loudness reached the MAL.

In 2 shows a preferred embodiment of the present invention, which is preferably contained in a hearing aid.

The processor unit 30 is a filter bank with a number of bandpass filters, e.g. B. in a parallel structure, preferably each mainly acting in one of the critical frequency bands, or is implemented as a unit for the fast Fourier transform. Attention is drawn to EP-0 661 905, in particular to the 12a to 16 , and directed to the respective description in relation to this filter bank, which is provided for the loudness correction on a single person "I", to which via the output converter 5 loudness-corrected sound signals are transmitted.

At output A of the processor unit 30 calculates the computing unit 70a according to a selected loudness model, the loudness L _I (S, P _I ) that the individual person "I" perceives and how it is processed by the processor unit 30 the hearing aid is corrected. The model parameters PI of the individual person, for example the parameters according to the Leijon model, are in the unit 70a entered, whereby EP-0 661 905 or S. Launer (see above) are to be regarded as inserted into the present application. In particular, attention is drawn to 15 as well as on the 3 to 9 and directed to the corresponding description of EP-0 661 905.

The signal input to the processor unit is similar 30 to a computing unit 70b performed in the same hardware unit as the unit 70a can be implemented and can actually be the same entity. There, according to the standard parameters P _N , as is also described in EP-0 661 905 and in Launer, which are also to be considered here as incorporated in the present description, the standard (N) loudness L _N (S, P _N ) of the incoming signal S is calculated. The output signal of the computing units 70 , which represents the loudness L _N or L _I , is in each case with a control unit 72 connected, in which the two loudness values are compared. The control unit 72 acts with its outputs on the control inputs E ₃₀ , which the loudness-relevant parameters P ₃₀ in the processor unit 30 , ie control in the respective filters of the filter bank contained therein. The perceived and calculated actual loudness LI is in the comparison unit 90 as a single time-varying value with that of the memory 110 output MAL value compared. The comparison result, ie the output signal of the comparator unit 90 , acts on an encoder unit 112 that generates a number of output signals that go to a weighting unit 114 in which the control unit 72 for setting the transfer function of the unit 30 output parameter values can be set further, thereby preventing L _I from rising above the MAL.

In 3 spectrum a) is one from the processor unit 30 output signal A over the z. B. shown in Barks scaled frequency. Spectrum a) leads to loudness L _Ia , as represented by the area that is well shaded under spectrum a) above the MAL value.

By the invention according to the 1 or 2 this is detected, the transfer function of the unit 30 z. B. is set in such a way that z. B. gives a signal A according to the characteristic b), which now and according to the hatched area under the characteristic b) corresponds to a loudness L _Ib well below the MAL.

By the present invention what is transmitted to the human ear Signal according to the psychoacoustic Loudness perception of the human ear and not by preselection any physical limits.

Claims (8)

Dependent method of limiting a signal transmitted to the human ear speed of an incoming sound signal, characterized by the following steps: - providing a limiting hearing device which generates a signal (A) from an incoming sound signal (S) which is transmitted to the human ear with a controllable transmission characteristic; - storing a threshold value (MAL) in the device; - generating in the device a signal dependent on the loudness (L (S, P); L _I (S, P _I )) of the transmitted signal; - Decreasing the loudness of the signal (A) transmitted to the ear by setting parameters of the transmission characteristic which determine the loudness (L; L _I ) of the signal transmitted to the ear (A) once the loudness (L; L _I ) of the transmitted signal (A) dependent signal reaches the threshold (MAL). A method according to claim 1, characterized by implementing the hearing device in a hearing aid. A method according to claim 1 or 2, characterized through the steps in which the transfer characteristic in dependence of the loudness perceived by a particular individual will and depending of the loudness perceived by a standard, individually is set. The method of claim 2 or 3, further comprising the steps of: - calculating the loudness (L _N (S, P _N )) perceived by a standard on a sound signal (S) input to the device; - The loudness (L _I (S, P _N )), which is perceived by the individual person at the sound signal, is calculated depending on the loudness of the transmitted signal (A); A desired hearing aid transmission characteristic is calculated from the calculated loudnesses of the standard or the individual person; - The transmission characteristic (T) of the hearing aid is set in accordance with the desired transmission characteristic; - The limitation is carried out by additionally setting the desired transmission characteristic depending on the loudness of the transmitted signal (A) and the threshold value (MAL). Hearing aid, with - an input sound / electrical converter ( 1 ), the output of which is operatively connected to the input - a signal processor unit ( 3 ; 30 ) with a controllable transmission characteristic (T), the output of which is operatively connected to an input of - an output converter ( 5 ) for the human ear, characterized in that there are provided: - a storage unit which can be set in advance ( 11 ; 110 ); - a computing unit ( 7 . 70a ), whose input matches the output of the processor unit ( 3 . 30 ) is operatively connected and which produces an output signal which depends on the loudness of a sound signal which is generated by the signal at the input of the output converter ( 5 ) is represented, whereby - the outputs of the computing unit ( 7 ; 70a ) or the unit that can be set in advance ( 11 ; 110 ) with corresponding inputs of a comparison unit ( 9 ; 90 ) are connected; - the output of the comparison unit ( 9 ; 90 ) with setting inputs (E ₃ ; E ₃₀ ) for the characteristics of the processor unit ( 3 ; 30 ) is connected. Device according to claim 5, characterized in that the transducers ( 1 . 5 ) and the processor unit ( 3 ; 30 ) Are part of a hearing aid. Apparatus according to claim 6, characterized by - a second computing unit ( 70b ) whose input matches the output of the input converter ( 1 ) is operatively connected and which generates an output signal that has a standard volume level in the input converter ( 1 ) represents the input sound signal; - The outputs of one and the other computing unit ( 70a . 70b ) with a third computing unit ( 72 ) are connected; - and the output of the further calculation unit ( 72 ) is operatively connected to the setting inputs (E ₃₀ ). Device according to claims 5 to 7, characterized in that the processor unit ( 3 ; 30 ) comprises a predetermined number of bandpass filters, each of which mainly acts in a corresponding spectral band, the setting inputs (E ₃ , E ₃₀ ) being operatively connected to the setting inputs of the filters.